Conjugated polymers (CP) hold great promises for next-generation bioelectronics, because of their good compatibility to biological systems, flexibility to fabrication and relatively low costs. Previous studies found that conjugated polymers could improve communications between electrochemical devices and biological systems initially; however, conjugated polymers, such as polyacetylene (PA), polyaniline (PANi), polypyrrole (PPy), polythiophene (PTh) and poly(3,4-thylenedioxythiophene) (PEDOT), are not originally designed for complex biological applications. When these synthetic polymers are used in biological systems, one major challenge is to keep a “clean” and biocompatible biotic-abiotic interface to minimize the foreign body reaction, reduce the infection, prolong the service life of the device, while maintaining materials' conductivity, stability and functionalities. The conventional conjugated polymers consist of hydrophobic or charged side chains. Biomolecules, mammalian cells and bacteria tend to attach to charged or hydrophobic surfaces. The adsorption of biomolecules and attachment of unwanted cells will reduce the sensitivity or lead to the failure of the embedded devices. To increase their biocompatibility, PTh, PANi and PPy hydrogels have been developed to combine the electrical properties from conjugated polymers with the properties of hydrogels. To gain the biocompatiblity, conducting polymers are blended or physically crosslinked with biocompatible and non-conducting polymers. For example, polyethylene glycol (PEG) was used to crosslink PANi for glucose sensing. However, non-conducting components compromise electrochemical properties of conducting materials. Furthermore, non-conducting components of current conducting hydrogels are not effective enough to prevent long-term biofouling and foreign body response. Previous study discovered that zwitterionic polymers could effectively resist nonspecific protein adsorption and cell attachment. In a previous study, an integrated poly(carboxybetaine thiophene) (PCBTh) both conducting and antifouling properties was developed. Due to the loosely packed polymer networks in these hydrogels, however, the electron conductivity of these materials are not yet suitable for applications that demand high electron/current transport.
It should be pointed out that much effort has been devoted to develop flexible, stable and biocompatible conducting polymers for CP based bioelectronic devices, but the starting materials used to form these conducting polymers are either poorly water-soluble or need the addition of surfactants to improve the aqueous processability. What is needed in the art is a method of forming flexible, stable and biocompatible conducting polymer coatings for bioelectronics devices that uses a monomer is that is highly water-soluble and can be directly polymerized in aqueous solution without using organic solvents or surfactants, while at the same time, maintaining electro-switchable antimicrobial/antifouling properties, excellent electrical conducting properties, increased biocompatibility, and improved bioelectronic performance.